Hydraulic press



5 Sh'ets-Sheet l Gttorneg March 14, 1933. w. ERNST HYDRAULIC PRESS FiledJune 27, 1929 March 14, 1933. w, ERNST HYDRAULIC PRESS l 1929 3Sheets-Sheet 2 Filed June 27,

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HYDRAULIC PRESS Filed June 27, 1929 5 Sheets-Sheet 3 k!) lmventor B @ai5M vmf ttor'neg-S,

Patented 14, 1933 UNITED STATES PATENT' OFFICE WALTER ERNST, F MOUNTGILEAD, OHIO, ,ASSIGNOR T0 HYDRAULIC PRESS MANUFACTURING COMPANY, 0FMOUNT GILEAD, OHIO y HYDRAULIC PRESS Application med June 27, 1929.Serial No. 373,985.

This invention relates to hydraulic presses which are intended to beoperated by fluid supplied under pressure from a constant dischargepump, and more particularly to that type of press which may be seteither to automatically perform' an indeterminate number of successivepressing operations, or to perform one complete pressing operation, atthe end of which the press platen is automatically brought to rest. Thepresent invention also embodies certain changes in and additions to thevalves and valve operating mechanism shown and described in myapplication for Letters Patent Serial No. 334,- 746, filed January 24,1929.

In the above named application I have 4 described a hydraulic pressconnected in a hydraulic circuit and arranged to be operated by fluidunder pressure delivered by a variable discharge rotary pump alsoconnected in the circuit, the valves and valve operating mechanismcontrolling the flow of uid in the circuit being so arranged that thepump is dischargeable in one direction only. By this arrangement,whereby the pump is dischargeable in one direction only, so that it isunnecessary to shift the heavy pump cross head in order to effect areversal of the direction of fluid travel in the circuit, 3o a highpress operating speed is attainable.

The valves and valve operating mechanism embodying the inventiondescribed in said application include a reversing valve located in thesurge tank and serving to control the direction of travel of highpressure fluid, and a pilot valve connected in a separate low pressurehydraulic circuit and havin connection to the reversing valve indepenently of the high pressure circuit for effecting move- 4o ments of thereversing valve to reverse the direction of travel of high pressurefluid. Platen-actuated mechanical means are provided for moving thecross head of the variable discharge pump to a neutral position when theplaten reaches the top of its upward or return stroke, thereby causingthe platen to dwell in its uppermost position until the high pressurereversing vvalve is shifted to produce a pressing stroke of the platen.It is to be noted that the ability of the platen to pump would notpermit its discharge being reduced to zero without completely stoppingthe pump. Therefore, when using a constant delivery pump in connectionwith a high pressure h draulic circuit similar to that outlined a ove,it is necessary that means be provided for diverting the higl `rpressurepump discharge away from the platen returning cylinders, and 'forby-pass ing the discharge directly into'the sur tank in order that theplaten will be broug t to a dwell in its uppermost position.

Accordingly, the main object of my invention is to provide means foroperating a hydraulic press including a high pressure circuit forproducing reciprocatory movements of the press platen, which circuit issupplied with fluid under pressure by a constant discharge pump, andmeans automatically operative when the platen reaches its uppermostposition for diverting the high pressure fluid from the platen returningcylinders and for returning the fluid directly to the surge tank.

Another 'object of the invention is to provide pressure responsive meansfor reversing the direction of movement of the press platen when thelatter encounters resistance to its downward travel irrespective of theposition of the platen, and separate means actuated by the platen andadjustable independently for causing the platen to automatically performan indeterminate number of pressing and return strokes or to cause theplaten to perform a single pressing stroke and a return stroke and tothen be brought to rest in its uppermost position. Other objects willbecome apparent from a reading of the following description, theappended claims and the several views illustrated in the drawings inwhich:

Fig. 1 is a front elevation of a hydraulic press showing some oftheoperating parts embodying my invention,

Fig. 2 is a central vertical sectional view of the upper end of a mainpressing c linder and a surge shifting valve mounted t ereon, Fig. 3 isa view showing the general piping arrangement in diagrammatlc form andshowing in section a b -pass valve and a platen-operated valve orcontrolling the movements of the by-pass valve,

Fig. 4 is a longitudlnal sectional view of a pilot valve,

Fig. 5 is a longitudinal sectional view of a reversing valve, and

Fig. 6 is a detail sectional view of one end of a piston valve'.

Fig. 7 is a fragmentar sectional view taken on the line 7-7 of Fpig. 4.

Fig. 8 is a detail view of a pilot valve actuating rod and associatedparts.

The invention may be embodied' in various types of hydraulic motors, butin the accompanying drawings it is illustrated in connection with apress of the four column downward presure type. Referring to thedrawings, there is shown a hydraulic ress A, having a base B, astationary table a press head D connected to said table by four strainrods E, and a reciprocatory platen F guided on the strain rods E in theusual manner.

It is to be understood that the present invention includes two entirelyseparate hydraulic circuits, one being a high pressure press operatingcircuit and the other being a low pressure pilot circuit. The lowpressure circuit is used to eilect the shifting of a reversing valve Ainthe high pressure circuit for producing resultant reciprocatorymovements of the press platen. These two circuits will be first outlinedand the various valves and valve operating mechanisms included in eachof the circuits will be subsequently described in detail.

With reference to the high pressure circuit, a constant discharge pump lis connected to a surge tank 2 by means of the suction pipe 3, as shownin Figure 3, and supplies fluid under high pressure to said circuit. Thedischarge of the pump is directed through a pipe line 4 which isconnected to the reversing valve 5. The valve 5 also has connected to itthe pipe line 6, which leads to booster cylinders 7 and to one side of asurge shifting valve '8 located in the surge tank 2, and a. pipe line 9which leads to push back or platen returning cylinders 10 and to theother side of the surge shifting valve 8. The reversing valve is locatedwithin the surge tank 2 and is provided with exhaust opeliingscommunicating with the surge tan The construction and the operation ofthe reversing valve 5 will be hereinafter described in detail, but forthe sake of clearnessit will, for the present, be sufiicient to say thatthe valve is adapted to be set' in either of two positions, in the firstof which positions the pipe line 4 is placed in communication with thepipeline 6, and the pipe line 9 With the sur e tank by means of one ofthe aforementioned exhaust openings, and in the second of whichpositions the pipe line 4 is placed in communication with the pipe line9, and thepipe line 6 with the surge tank by the other of theaforementioned eX- haust openings. v

The 'low pressure pilot circuit includes a pipe line 11 whichcommunicates with the surge tank, a low pressure pump 12 arranged toreceive its intake from the pipe line 11, and a low pressure dischargepipe line 13 connected to the pump and to a pilot valve 14. A pipe line15 connected to the pilotl valve and to the surge tank 2 alordscommunication therebetween, and it will thus be seen that the pipe line11, the pump 12, the pipe line 13, the pilot valve 14, the pipe line 15,and the surge tank 2 comprise the entire low pressure hydraulic pilotcircuit. Separate pipe lines 16 and 17 connect the pilot valve to apressure responsive valve actuating device G associated with thereversing valve, but it is to be noted that the pipe lines 16 and 17form no part of the low pressure circuit. The pilot valve is so arrangedthat, upon being shifted in one direction, fluid under pressure from thelow pressure pilot circuit will be introduced through the pipe 16 intoone side of the. pressure responsive valve actuating means G to shiftthe reversing valve in one direction, and when the pilot valve isshifted in the opposite direction fluid under pressure from the lowpressure pilot circ/uit will be introduced through the pipe line 17 intothe opposite side of the pressure responsive valve actuating means G andwill move the reversingrvalve in the opposite direction.

he surge shifting valve 8 is provided with a valve casing 18 having avalve chamber 19 which communicates with the surge tank 2 by means of aport 20, and with the main cylinder 21 of the press by meansof a port22. Slidably mounted in the chamber 19 is a balanced piston valve 23,said valve being provided at one of its ends with a tail rod 24, thetail rod being slidable in a bore 25. The bore 25 communicates with thechamber 19 by means of a passage 26, and also with the pipe line 6. Thevalve 23 is also provided with a second tail' rod 27 which extendsthrough a chamber 28 into a bore 29 in a casing 3() attached to thecasing 18 and into a chamber 31 in said casing 30, the chamber 31communicating at its outer end with the pipe line 9. It may be notedthat, when the piston valve 23 is in the position shown in the drawings,the main cylinder 21 communicates with the surge tank 2 by means of theport 22, the chamber 19, and the port 20, but, when the piston valve iscaused to be shifted to the left in a manner to be hereinafterdescribed, the cylinder21 will communicate with the pipe line 6 by meansof the port 22, the chamber 19 the passage 26, and the bore 25.

Mounted on the top of the valve casing 18 and adapted to communicatewith the chamber 28 is a check valve 32, which comprises a casing 33having ports 34, 34, and 35 and a valve ball 36 which is urged to closedosition by a spring 37, the tension of whlch spring may be adjusted bymeans of a threaded plug 38 for a purpose hereinafter specified. It isto be noted that, When the piston valve 23 is moved to the left in the,plane of the drawings, fluid contained in the chamber 28 will beexpelled through the check valve 32 into the surge tank 2, but that nofluid will enter the chamber 28 through said check valve at any time.

Mounted on the bottom of the casing is a second check valve 39 adaptedto communicate with the chamber 28 by means of a port 40 and with thesurge tank 2 by means of a port 41. A valve ball 42 in the check valve39 is kept seated by gravity, and by the pressure in the chamber 28, sothat when the piston valve 23 moves to the right in the plane of thedrawings the ball will be lifted from its seat by the suction created inthe chamber 28, thus allowing iuid to flow from the surge tank 2 throughthe ports 41 and 40 into the` chamber 28.

With more particular reference to the reversing valve 5, there is shownin Figure 5 a valve casing 42 having a central chamber 43 anda pistonvalve 44 slidable longitudinally ,in the chamber and provided at itsopposite ends with valve heads 44a and 44h. In order to facilitate theconnecting of the reversing valve tothe pipe lines 6 and 9, there areprovided detachable plates 45 and 46 bolted to the valve casing 42a,shoulders 47 on said plates fitting within counter bores 48 in the valvecasing, and clamping packing 49 in said bores, thus forming a pressuretight joint between the casing and the plates. The plates are providedwith threaded bores which receive the ends of the pipes 6 and 9, andthese bores register respectively with ports 50 and 51 formed in thevalve casing 42a. A similar plate 52 is bolted to the valve casingmidway between the ports 50 and 51 and is providedv with an opening 53which communicates with the chamber 43, and in which opening the pipeline 4 is connected. It will be apparent that, when the piston valve 44is in the position shown in Figure 5, the pipe line 4 will communicatewith the pipe line 6 by means of the openingor port 53, the valvechamber 43, and the port 50. When the piston valve is moved tothe leftthe pipe line -4 will be placed in communication with the pi e line 9 bymeans of the opening 53, the va ve chamber 43, and the port 51.

Whemthe valve is in the osition shown in Figure 5, and the pipeline 4 isin communication with the pipe line 6, it is necessary that the pipeline 9 be placed in communication with the surge tank. To this end, thevalve head 44a is rovidedwith `an annular recess 54 arrange tocommunicate with a transversely disposed opening 55 eX- tendin inwardlyfrom said annular recess towar s the center of the valve head 44a andcommunicating with a ort 56 formed in the valve and extendin rom thetransverse opening 55 to the a jacent outer end of the piston valve. Theouter end of the port 56 is enlarged and threaded to receive a removableplu 56a having a central opening 56 exten ing longitudinallytherethrough to register with the opening 56.' It will be seen that iuidin the pipe line 9 will enter the annular recess 54, then pass into the'transverse opening 55, and then out through the port 56 and the openingin the plug and into the-surge tank, the end of the piston valve 44being constantly exposed to the fluid in the surge tank. vWhen thepiston valve is moved to the left in the plane of the drawings, theannular recess 54 will be moved to the left of the port 5l as viewed inFigure 5 and communication between the pipe line 9 and the surge tankwill be thereby cut oil". It is now necessary that, with the valve inthis new position, the pipe line 6 be placed in communication with thesurge tank. For accomplishing this purpose I provide the valve casingwith a chamber 57 located to the right of the piston valve and alsoprovide said chamber with a plurality of relief openings 58 extendingthrough the valve casing and communicating with the surge tank. When thepiston valve has moved to the left, the valve head 44b will move to theleftof the port 50, and the pipe line 6 will be placed in communicationwith the port 51, the valve chamber 43, the chamber 57, and the openings58.V Y

Inasmuch as the pump 1 is arranged to deliver a continuous discharge itis desirable that the reversing valve be so constructed that the ports50 and 51 will not be completely covered simultaneously by the valveheads 44b and 44a respectively when the piston valve 44 is in anintermediate position while being shifted from one extreme position tothe other, because if these ports were so simultaneously covered, thedischarge of the pump would be entrapped between the valve heads and thepump, and associated piping would be subjected to a severe momentaryshock. In order to avoid the entrapping of the pump discharge when thevalve is being shifted, the port 50 is made wider than the valve head441 and the port 51 is made wider than either of the portions of thevalve head 44* which lie on opposite sides of the annular recess 54.`Because of this construction, when being shifted from one extremeposition to the other, the valve heads will at no time completely coverthe ports 50 and 51 so that it is impossible to entrap the pumpdischarge between said heads. Thus, when the iston valve is moved to theleft from its igure 5 osition to an extent. 'ust slightl greater t anthe width of the ead 44", t e pump discharge will communicate with thepipe line 6, the pipe line 9 and with the surge tank by means' of thechamber 57 and the ports 58, and also by means of the opening 55, theport 56, and the opening 56". When the piston valve has moved farther tothe left so as to cut olii' communication of the pump with the opening55, and with the chamber 57, fluid under pressure will be delivered tothe push back cylinders through the pipe line 9.

For guiding the right hand end of the iston valve when the head 44" ispositioned etween the walls of the port 50, the valve is provided with aplurality of radially disposed longitudinally extending ribs 59 adaptedto slide in the valve casing and to thereby maintain the piston valvecentrally in the valve chamber.

For shifting the valve 44 in either direction, I provide the pressureresponsive valve actuating means G located at the outer end of thereversing valve. This valve actuating means includes a ressure chamber60 formed in the outer en of the valve casing 42, a port 61communicating with the inner end of the chamber 60 and with the pipellne 16, a port 62 communicating with the outer end of the chamber 60and with the pipe line 17, a iston rod or stern 63 extending from the vave 44 and into the chamber 60, and a piston 64 fixed to the outer end ofthe rod 63 and mounted for reciprocatory movements in the chamber 60. Itis apparent that, when fluid under pressure is admitted from the lowpressure pilot circuit through the pipe line 17 and into the outer endof the chamber 60, the piston 64 will be movedto the left as viewed inFig. 5, and the valve 44 will be shifted to place the pipe line l4 incommunication with'the pipe line 9, and the pipe line 6 in communicationwith the surge tank. In a similar manner, when fluid under pressure isadmitted from the low pressurel pilot circuit through the pipe line 16and into the inner end of the chamber 60, the piston 64 and the valve 44will be returned to the position shown in Figure 5, thereby lacing thepipe line 4 in communication with the ipe line 6, and the pipe line 9 incommunicatlon with the surge tank.

The pilot valve 14 is used to direct Huid from the low pressure pilotcircuit lirst into the pipe line 16 to shift the piston valve 44 to theright as viewed in Figure 5, and then to introduce fluid under pressurefrom the i low pressure pilot circuit into the pipe line 17 to shift thepiston valve 44 to the left. The ilot valve shown in detail in Fig. 4,inclu es a valve casin 65 formed with a valve chamber 66, whic chambercommunicates with the port467 formed 1n' the casing. The chamber 66 isalso arranged to communicate with the pipe line 16 by means of an outletport 68 and to communicate with the pipe line 17 by means of an outletport 69. Slidably mounted in the bore forming the chamber 66 is a pistonvalve 70 having a stem 71 extending from one end of the valve throu hpacking 72 held in place by a gland nut g3 threadably mounted in an endcap 74 secured to the outer end of the valve casing. The stem 71 extendsthrough and somewhat beyond the gland nut 73Y and is rovided with aflange 75 located within t e valve chamber and ada ted to abut aninwardly extending fiange 6 on the end ca 74, thus limiting the travelof the valve 0 to the right. When the valve 70 is in the position shownin the drawin s, that is, in its extreme right hand posltion, the pipeline 13, receiving fluid from the low pressure pum 12, will communicatewith the pipe line 1 by means of the port 67, the valve chamber 66, andthe port 69, whereas, when the valve 70 is moved to the left, the pipeline 13 will communicate with the pipe line 16 by means of the port 67,the valve chamber 66, and the ort 68.

en the valve 70 is in the position shown in Figure 4, in which positionof the valve the pi e line 13 communicates with the pipe line 1 it isnecessary that thepipe line 16 communicate with the surge tank in orderthat the pressure acting through thepipe line 17 may be able to move thepiston 64 of the reversing valve. To this end I rovide the pilot valvewith a port 77 w ich communicates with the valve chamber 66 and with thepipe line 15, which pi line is in constant communication with t e sur etank, and a cored passage 78 formed in t e valve casing to connect theend portions of the chamber 66 located on opposite sides of the pistonvalve 70. When the valve 70 is in the position shown in Figure 4, thepipe line 16 will communicate with the pipe line 15 by means of the port68, the valve chamber 66, the cored passage 78, and the port 77. Whenthe piston valve 70 is moved to the left in the plane of the drawings,the pipe line 17 will communicate with the pipe line l5 bymeans of theport 69, the valve chamher 66, and the port 77.

As stated above, the pipe lines 16 and 17 leading-from the pilot valveto the chamber 60 in the reversing valve do not form a part of the lowpressure circuit, and, after fluid under pressure acting through eitherof these pipe line 13 by means of a' pipe lines has acted to shift thepiston 64, .cation with the surge tank by means of the there will be nofurther flow of fluid through cored passage 91, the port 84, the coredpaseither of said pipe lines. Since the low sage 78, the port 77, andthe pipe line 15, pressure pump delivers a continuous disso that thestatic pressure of the fluid in charge, it is necessary that means beprothe surge tank acts upon the outer end of vided vfor directing thedischarge of the the plunger 79 and thus aids the spring 88 pump intothe surge tank during interto urge the plunger to its closed position.vals between movements of the piston Rigidly fixed to the valve casing65 is a. 64. For accomplishing this purpose the separate casing 92,which casing is provided pilot valve 14 is provided with a reliet` witha chamber 93 and with inwardly exvalve H. This relief valve includesa-plungtending lianges 94 and 95 concentrically er 79 slidably mountedin a sleeve 80 rigaligned with the valve chamber 66 of the idly mountedin a bore 81 formed in the pilot valve. Slidably mounted in the casvalvecasing and adapted to communiing 92 is a valve actuating plunger 96. Thecate with the port 67 and the pipe line 13 plunger 96 is provided with astem 97 which by means of a port 82. The sleeve 81 is projects into thevalve chamber 66 of the provided with an opening 83 extending pilotvalve, and a flange 98 on the plunger through the wall of the sleeve andcomis adapted to seat in a recess 99 formed in a municating with a port84 formed in the bushing 100 mounted in adjacent and convalve casing tocommunicate with the valve centric counter bores 101 and 102 in thecaschamber 66 at the inner end thereof. The ings 92 and 65, thuslimiting the movement plunger 79 is provided at one of its ends of theplunger 96 in one direction. The with a lar ge 85 adapted to abut aninwardplunger 96* is also provided with another l v extending flange 86formed in the valve stem 103 extending through packing 104 and casingand to thus limit the movement of' agland nut 105 screw threaded into anopentlie plunger in one direction. The valve ing 106 in the end of thecasing 92. The casing 65 is further provided with a. spring outer endportion ,of the stem 103 is threadchamber 87 concentrically arrangedwith the ed to receive a hand wheel 107, and interplunger 79, andpositioned within this posed between the hand wheel and the gland.spring chamber is a coiled spring 88 internut 105 is a coil spring 108and a spring posed between the end of the plunger 79 and Seat 109. Thehand Wheel 107 iS SCleWed a. threaded plug 89 screw threaded into the onthe stem 103 to place the spring under spring chamber, the springserving to urge compression so that the hand wheel, the stem the plunger79 to a closed position, in which 1,03, and the plunger 96 will beconstantly position the inner end portion of the plungyIged outwardly. Asecond and smaller er extends past the Slot 83 A hollow nut hand Wheel110 lS SCleW threaded 0I1 the @11d 90 is screw threaded on the plug 89for cov Y, 0f the Stein and drawn u tight against the ering the latter,and also serves as a lock hand wheel 107 for locking the latter and nutto retain the plug 89 in adjusted posiretalning 1t against accidentaldisplacement tion. The port 84 communicates with the from its adjustedposition.

spring chamber 87 by means of a cored pas- The plunger 96 is of slightlygreater disage 91. When the piston valve is moved anleter than the stem103 and forms thereto the left, fluid will be admitted from the with aresultant shoulder 111, which shoulloW Pressure pilot, circuit, throughthe pipe del 1S at all times (llSpOSed Within the Chamline 13, the port67, the valve chamber 66, ber 93 Connected to the casing 92 and the port68, andthe pipe line 16 into the arranged to communicate with thechamber inner end of the chamber 60 in the revers- 93 there/1I! iS aplpe 112 Which is also coning valve, thereby moving the piston 64 toDeCedO the Plpe line 6 S0 Phat the Chamber the right, as viewed inFigure 5. When the 93 is in constant. communication with the pieton 64has been moved to its extreme right Plpe llle 6- It Wlll be apparentthat, When hand position so that there can be no furthe PlS'OIl ValVeO0f the. P1 lot Valve is in ther flow of fluid through the pipe /line 16,ltS left hand position, a building up of presthe pressure in the lowpressure pilot circuit Sure 1n the pipe line 6 will result in a corwillbuild up and will move the relief valve Ie-SPOIldlIlg bulldlllg 11p 0fpressure in the plunger 79 against the pressure exerted by Chamber 93,and When a predetermined presthe spring 88 until the inner end of theSure has been reached, which pressure is plunger has moved to place theport 82 in determined by the amount of pressure excommunication with theport 84 by means of erted by the spring 108, the plunger 96 will theopening 83, at which time the low presbe moved to the right in the planeof the sure fluid will be discharged from the pipe drawings until thestem 97 carried by the line 13 through the ports 67 and 82, the plungerengages the piston valve 70 and opening 83, the port`84, the coredpassage moves it to the right, that is, moves it into 7 8, the port 77,and the pipe line 15 into the position shown in Figure 4.

the surge tank. It is to be noted that the For moving the piston valve70 tothe left spring chamber 87 is in constant communias viewed inFigure 4,1 provide mechanical platen actuated means adapted to engagethe end of the stem 71.

Referring to Figure 1, there is shown a vertically disposed operatingrod 113 slidably mounted in lugs 114 and 115 on the stationary table Cand the press head D respectively, the downward movement of said rodbeing limited b a collar 115 adjustably fixed to the ro The rod 113 isconstantly urged to its lowermost position by gravity, and also by meansof a coiled spring 116 mounted on the rod between the lug 115 and acollar 117 also on said rod. A boss 118 fixed to the platen F sarrangedto slide freely on the rod 113. Adjusta l mounted on the rod 113 is acollar 119 whic is adapted to be engaged by the boss 118 Slidablymounted in the recess 120 is a rod' 122 provided with a pin 123 whichextends through and is rigidly attached to the rod, and has its oppositeend portions projecting through the slots 121. A coil spring 124 islocated in the recess 120 and is dis osed between the bottom of therecess an the inner end of the rod 122, `the spring constantly urgingthe rod to its uppermost position, in which position the pin 123contacts with the upper end walls of the slots 121. A bell crank lever125 is pivotally connected to the press head D as at 126. One arm 127 ofthe bell crank lever is pivotally connected to a head 128 on the rod 122as at 129. The other arm 130 of said lever is provided with .a roundedhead 131 adapted to engage the stem 71 of the pilot valve and to move itinwardly when the rod 113 is lifted. The spring 124 urges the rod 122 toits uppermost position at all times, and serves as a cushion forrelieving the pilot valve of any undue shock which might otherwise occurif the connections between the operating rod and the valve stem wererigid.

Attention is called to the fact that, al-

.though the piston valve of the pilot valve has no permanent connectioneither to the stem 97 or to the bell crank lever 125, the piston valveis disposed in a horizontal plane and will be retained in either of itspositions by the frictional contact of the packing 72 with the stem 71,until said piston valve is positively shifted in the manner describedabove.

A manually operable lever 132 is pivotally mounted on the base B as at133, and one arm 134 of said lever is provided with a rounded head 135adapted to engage the lower face of a collar 136 xedly mounted on theoperating rod 113 and to lift said rod when the lever is swung in aclockwise direction as viewed in Figure 1. A coil sprin 137 interposedbetween the base B and t e arm 134 of the lever tends to cause a lu 138on said lever to abut a lug 139 on the ase, thereby norniallymaintaining the lever in the position shown in. Figure 1. It is to benoted that, when the rod 113 is caused to perform a reciprocatory motionduring automatic operation of the press, the collar 136will move towardsand away from the he'ad 135 and there will be no danger of the lever 132swinging outwardly and striking the operator.

It is to be noted that the piston valve 44 of the reversing valve 5 isadapted to be moved into two extreme positions for producingreciprocator'y movements of the platen, and that the means provided formoving the piston valve is adapted to move it from one extreme positionto the other, but is not adapted to maintain the valve in a neutralposition for continuously directing the discharge of the pump into thesurge tank. For this reason,.in order that the platen may be brought torest at the end of its return stroke when desired, means must beprovided for diverting the discharge of the high pressure pump away fromthe reversin valve.

To this end I provide the discharge line 4 of the high pressure circuitwith a bypass valve I, which includes a valve casing 140, a valvechamber 141 within the casing, and a piston valve 142 slidably mounted1n the chamber and having spaced heads 143 and 144 located at oppositeends of the piston valve. As shown in Figure 3, the valve chamber isopen at its left hand end, is closed at its right hand end, and adjacentthe latter end of the casing is provided with a port 145 communicatingwith the sur e tank. Intermediate the port 145 and t e open end of thevalve chamber the latter communicates with the pipe line 4. It will beobserved that when the'piston valve is in the position shown` in Figure3, the discharge of the pump 1 will be blocked by the heads 143 and 144of the valve, so that fluid will be directed to the reversing valve 5.When the piston valve is moved to the right as viewed in Figure 3, thehead 144 will pass beyond the port 145 and will place the pipe line 4 incommunication with the surge tank 2 bymeans of the valve chamber 141 andthe port 145. The fluid discharged from the pump 1 will then be divertedfrom the reversing valve and will be returned to the surge tank.

Pressure responsive means, to be later described, are provided foropening the bypass valve I to divert the pump discharge from thereversing valve when the platen reaches the end of its return stroke.-At

this time the push-back cylinders will be filled with fluid, and, inorder that the weight of the platen will not cause the latter to coastdownwardly and expel the fluid from the push-back cylinders and thereversing valve, the pipe line 4 is provided with a check valve 145aarranged to permit flow of fluid from the pump to the reversing valve,but to prevent flow of fluid from the reversing valve. to the by-passvalve I- -The pressureresponsive means for actuating the by-pass valveincludes a pressure chamber 146 formed in one end of the valve casing140, a piston 147 slidably mounted in the chamber, and a stem 148connecting the piston to the piston valve 142. Hydraulic Vconnectionsincluding a pipe line 148, a

platen actuated valve 149, and pipe lines 150 and 151 communicating withopposite ends of the pressure chamber 146, are connected between the lowpressure pilot circuit and the chamber for actuating the piston 147.

The platen actuated valve includes a casing 152, a valve chamber 153therein, a piston valve 154 mounted for sliding movements in thechamber, a spring 155 interposed between one end of the-piston valve andone end of the chamber for urging the 4valve toward the left, and a stem156 extending through an opening in the other end of the casing andadapted to be actuated by platen operated means for moving the valvetoward the right against the pressure of the spring. The right hand endof the valve chamber is vented by means of an opening 157 extendingthrough the piston valve, and a pipe 158, which affords constantcommunication between the surge tank and the left hand end of the valvechamber.

When the piston valve 154 is in the position shown in Figure 3, pressurefluid from the low pressure pilot circuit will be directed into theright hand end of the pressure chamber 146 by means of the pipe 1485,the valve chamber 153, and the p1pe 151, thereby maintaining the pistonvalve 142 of the by-pass valve in the position shown in Figure 3. Whenthe piston valve 154 of the platen actuated valve is moved to the right,pressure fluid ,from the low pressure circuit will enter the left handend of the pressure chamber 146 by means of the pipe 1482*,'the valve'`chamber 153, and the pipe 150, thereby moving the piston valve 142 ofthe -by-pass valve toward the right, thus diverting the discharge of thehigh pressure pump from the reversing valve and returning the fluid tothe surge tank.

For moving the piston valve 154 to the right against the pressure of thespring 155, I provide mechanical platen-actuated means adapted to engagethe end of the stem 156. As shown in Figure 1, these means include avertically disposed operating rod 159 slidably mounted in lugs 160 and161 on the stationary table C and the press head D, respectively, thedownward movement of the rod being limited by a collar 162 adjustablyfixed to the rod and adapted to abut the lug 160. The rod is constantlyurged to its lowermost position by gravity, and also by means of acoiled Spring 163 mounted on the rod between the lug'161 and a collar164 also on the rod. A boss 165 xed to the platen F is arranged to slidefreely on the rod 159 and is adapted to engage a collar 166 on the vrodwhen the platen has reached a predetermined point in its u ward travel,thereby lifting the rod. A be l crank lever 167 pivotally connected tothe press head D as at 168 has one of its arms pivotally connected tothe rod 159. The other arm thereof Iis provided with a rounded head 169adapted to engage the stern 156, of the platen actuated valve and tomove it inwardly against the pressureof the spring 155 when the rod 159is lifted.

The upper end of the rod 159 is provided Awith spring .cushioning meansidentical to those with which the rod 113 is provided. Since said meanshave been described in detail in connection with the description of therod 113, it will not be necessary to describe them again in connectionwith the rod 159.

Operation If it is desired that the press operate under full automaticcontrol, the collar 119 is adjusted to such a position on the operatingrod 113 that the collar will be engaged by the boss 118 on the platen asthe platen approaches the end of its upward or return stroke, and themotor driving the pump will then be started.

Assuming that this adfustment of the collar 119 has been made, t at themotor driving the pump has been started, and that the reciprocatoryplaten is traveling downward, the piston valve 44 of the reversing valve5 will be in the position shown in Figure 5 and the piston valve23 ofthe surge shifting valve 8 will be in the position shown in Figure 2,and the operation of the various parts comprising the. automatic controlmechanism will be as follows:

The pump 1 is set to discharge fluid under pressure through the pipeline 4 into the reversing valve 5, the Huid passing from the pipe line 4through the port 53, the valve chamber 43, the port 50, and the pipeline 6, and into the booster cylinders 7, the fluid pressure therebyexerted in said booster cylinders causing the platen to move downwardly.During this part of the down stroke of the platen, fluid vfrom the surgetank 2'will flow through the port-20, the valve chamber 19, and the port22 into the main cylinder 21. While the down stroke of the platen isbeing performed the fluid which entered the push back cylinder 10 duringthe` preceding up stroke must esca e from said cylinders into `the surgetal This is accomplished by means of the pipe line 9, the port 51, andthe openings and 56 in the piston valve 44.

lVhen the laten encounters resistance to its downwar movement, the fluidpressure in the ipe lines 4 and 6 will build lup until it reac es apredetermined value, at which time said pressure, acting on the tail rod24 of the surge shifting valve 8, will cause the piston valve 23 to moveto the left from the position shown in Figure 2, thereby expelling thefluid contained in the chamber 28 through the ports 35 and 34 of thecheck valve 32. It is to be noted that, by adjusting the lug 38 to varythe pressure exerted on the all 36 by the spring 37, the fluid pressureinthepipe line 6 necessar to move the piston valve to the left mayvaried at will.

After the piston valve 23 has been moved to the left as described above,the valve chamber 19 will be shut olf from communii cation with the port20 by the right hand end portion of said valve, and at the same timesaid valve chamber 19 will be placed in communication with the pipe line6 by means ofthe passage 26 and. the bore 25, which bore has beenvacated by the tail rod 24. The main cylinder 21 now receives fluidunder pressure from the valve chamber 19 through the port 22. As hasbeen heretofore stated, the chamber 93 of the pilot valve 14 is inconstant communication with the pipe line 6 by means of the pipe 112, sothat, when the platen encounters further resistance to its downwardtravel resulting in a further building u of pressure in the highpressure circuit, t e pressure will increase correspondingly in saidchamber until a predetermined pressure has been reached, at which timethe plunger 96 will be moved to the right by the pressure in saidchamber and against the force of the spring 108.

It is to be understood that, while the platen has been descending toperform its pressing stroke, the piston valve 70 has been in .a positionto the left of that shown in Figure 4, so that the pipe line 13 of thelow pressure circuit has been in communication with the pipe line 16.Since the iston valve 44 has been stationary during this pressing strokeof the platen, fluid from the low pressure circuit has not been flowingthrough the pipe line 16, but the discharge of the pump 12 has beenby-passed by means of the relief valve and returned to the surge tank inthe manner described above. When the plunger 96 of the pilot valve 14 ismoved to the right as viewed in Figure 4, the stem 97 will contact thepiston valve 70 and move said valve to the position shown in Figure 4.Fluid from the low pressure circuit will ,into the pressure chamber onow pass through the pipe 13 and the pipe 17 into the right hand end ofthe pressure chamber 60 of the reversing valve 5 and will force `thepiston 64 to the left as viewed in Figure 5, thus shifting thepistonvalve 44 to place the port 53 in communication with the pipe line9. In this new position of the piston valve 44, the pipe line 4 willcommunicate with the push back cylinders ,10 by means of the port 53,the valve chamber 43, the port 51, and the pipe line 9, and the pipeline 6 will communicate with the chamber 57 so that the boostercylinders will communicate with the surge tank by means of the pipe line6, the port 50, the chamber 57, and the openings 58.

Fluid under pressure in the pipe line 9 and in the chamber 31 of thesurge shifting valve will now act on the tail rod 27 causing the pistonvalve 23 to be moved to the right, or, in other words, to the positionshown in Figure 2. While the piston valve is moving to the right, fluidfrom the surge tank 2 will enter the chamber 28 through the check valve39, as hereinbefore described. The` iuid under pressure entering thepush back cylinders 10 from the pipe line 9 causes the platen to moveupwardly, and the fluid in the main cylinder 21 will be expelledtherefrom into the surge tank through the port 22, the valve chamber 19,and the port 20. During the upward movement of the platen, fluid will beex elld from the booster cylinders through t e pipe line 6, the port 50,the valve chamber 43, the chamber 57 the openings 58, and into the surgetank 2.

When the platen approaches the limit of its return stroke, the boss 118carried by the platen will strike the collar 119 on the operatingrod113, lifting the operating rod and causing the bell crank level 125 tobe swung in a clockwise direction as viewed in Figures 1 and 8, therebyforcing the stem 71 of the pilot valve inwardly and shifting the pistonvalve thereof to the left as viewed in Fi re 4. e

n this position of the piston valve 70, fluid will pass from the lowpressure circuit through the pipeline 13, the Valve chamber 66 of thepilot valve, and the pipe line 16 the reversing valve, thereby movingthe piston 64 to the right as viewed in Figure 5, and shifting thepiston valve 44 to the position shown in Figure 5. With the valve 44 inthis position, the laten will begin another pressing stroke whlch willbe performed in the same manner as the one already described, andobviously the press will continue to operate in this manner as long asthe motor driving the pump is runnin When it is desired that the pressoperate semi-automatically, that is, in such a way that the platen willperform one pressing operation and then return to its uppermost yy1,901,291 t the return stroke will be executed in the same A manner asthat described in connection with the fullautomatic operation of\\thepress. When the platen has reached afpredetermined point on its returnstroke, the boss 165 will engage the collar 166 and raise the rod 159,thereby rocking the bell crank lever 167 in a counter-clockwisedirection as viewed in Figure 1, thus moving the stem 156 to the left asviewed in Figure 1 and to the right as viewed in Figure 3. Pressurefluid from the low pressure pilot circuit will then be admitted to theleft hand end of the pressure chamber 146 and willmove the piston valve142 of the by-pass valve to the right, thereby diverting the dischargeof the pump from the reversing valve and returning it to the surge tank.With the valve 142 in its right hand position, fluid discharged by thepum will be freely bypassed to the surge tan through the medium of thepipe 4, the valve chamber 141, and the port 145. It will be noted thatthe piston valve 142 is movable to a definitely closed position as shownin Figure 3 and to a definitel and fully open position when moved-to t eright from the position shown in Figure 3. This movement from the closedto the full open position will be uninterrupted, sot at, when once theplaten has reached a point suicient to cause opening of theplaten-controlled valve 154, the by-pass` valve 142 will be completelyopened to by-pass fluid to the surge tank at substantially no pressure.As a result of this uninterrupted opening movement of the valve, therewill be no time in which the pump discharges against a throttled orrestricted bypass. As has already been described, the check valve 145will, at this time, maintain the fluid in the push-back cylinders sothat the platen will be held at rest. If, however, there should be someleakage in the system, so that some of the fluid in the push-backcylinders escapes therefrom, the platen will begin to descend. As soonas the platen has descended to an extent to perthen act to close theby-pass valve so that' fluid from the high pressure pump will bedirected to the reversing valve and the pushi.:

back cylinders until the platen has been returned-to its uppermostposition, at which time the by-pass valve wil 'again be opened. It istherefore apparent that the by-pass valve I, the valve 149 and the checkvalve 145 are Aso arranged as to maintainthe platen at or near the upperend of its stroke until the reversing valve is` shifted to cause theplaten to erform another vpressing stroke, even if t ere are some leaksin the system...

To cause the platen to. erform another pressing stroke, the lever 32 isswun toward the right, thereb raising the ro 113 and moving the stem g1of the ilot valve inwardly. This results in the s ifting of the pistonvalve 44 to the position shown in Figure 5, thus placing'the pipe line 4in communication with the ipe line 6 and with the booster cylinders. heplaten will then start downwardly on its pressing stroke and will bereturned to its upper position and again brought to rest inthe manneralready described.

Although I have illustrated a press provided with a platen especiallyadapted for lperforming compressing operations it is to be understoodthat the invention described herein may be embodied in presses used forpunching, forging shearing, or other like purposes. and t at the termplaten is intended to cover any tool, die, or other appliance with whicha press embodying my invention might be provided. Other modifications inconstruction and arrangement of parts may be also made; withoutdeparting from the scope of my invention.

I claim:

1. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic circuit; a reversing valveV operatively connectedin said circuit for controlling the direction of movement of the platen;means for moving the reversing valve when the platen reaches the end ofits pressing stroke to effect a return of the platen; a by-pass valveoperatively connected in said circuit and adapted to open when theplaten reaches the end of its return stroke for diverting the pressureiuid from the press to thereby bring the platen to rest at the end ofthe return stroke thereof simultaneously with ,the continued dischargeof the pump; and mit the operating rod 159 to be lowered and hydraulicmeans controlled by the platen for operating said by-pass valve from itsclosed to its fully open position and vice versa.

2. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic circuit; a reversing valve operatively connected insaid circuit for' controlling the direction of movement of the platen;means for moving the reversing valve when the platen reaches the end ofits pressin stroke to effect a return of the platen; an

a by-pass valve operatively connected in said circuit and adapted whenopen to divert the pressure fluid from the press to thereby bring theplaten ltorest; fluid preure responsive means connected to said by-passvalve and ada ted to move the latter from its closed to its full o enposition; and means for supplying ui under pressure to said pressure'responsive means when the platen reaches a predetermined point on itsreturn stroke to move the by-pass valve to its fully open osition.

3. The com ination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic circuit; a. reversing valve operatively connectedin said circuit for controlling the direction of movement of the platen;means for moving the4 reversing valve when the platen reaches the end ofits pressing stroke to effect a return of the platen; and a bypass valveoperatively connected in said circuit and adapted when open to divertthe pressure fluid from the press to thereby bring the platen to rest; apressure chamber; a reciprocable piston mounted therein and connected tothe by-pass valve and adapted to open and close the latter; meansadapted to be connected to a source of fluid pressure and ada ted to beconnected to said chamber on either side of the piston; and meanscontrolled by the platen for directing pressure fluid to the chamber onone side of the piston to move the by-pass valve to its fully openposition, and for directing fluid to the chamber on the opposite side ofthe iston to close said valve.

4. T e combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic circuit; a reversing valve operatively connected insaid circuit for controlling the direction of movement of the platen;means for moving the reversing valve when the platen reaches the end ofits pressing stroke to effect a return of the platen; and a bypass valveoperatively connected in said circuit and adapted when open to divertthe pressure fiuid from the press to thereby bring the platen to rest; apressure chamber; a reciprocable piston mounted therein and connected tothe by-pass valve and adapted to open and close the latter; a source offluid pressure; hydraulic connections between said source and thechamber and including a platen operated valve interposed between theby-pass valve and said source of pressure, said platen operated valvebeing normally in a position to direct pressure liuid to said chamber onone side of the piston to maintain the by-pass valve closed; and meansadapted to cooperate with the platen and the platen operated valve tomove the latter to a position wherein pressure fluid will be directed tosaid chamber on the other side of the piston to move the by-pass valveto its fully open position.

5. The combmation with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic press-operating circuit; a reversing valveoperatively connected in said circuit; a source of fluid pressure; apilot valve operatively connected to said source of iiuid pressure;pressure responsive valve-actuating means associated with said reversingvalve; means adapted to provide fluid communication between the pilotvalve and said valve actuating means for admitting fiuid from saidsource of pressure to said valve-actuating means to shift t-he reversingvalve when the pilot valve is shifted; means for shifting the pilotvalve when the platen approaches the end of its pressing stroke; a

by-pass valve in said press operatin circuit adapted when open to divertfluid rom the press during continued discharge of the pump; fluidpressure responsive means associated with said by-pass valve and adaptedto have communication with said source of pressure; and platen operatedmeans for establishing communication between said source of pressure andsaid fiuid pressure responsive means when the platen approaches the endof its return stroke for opening the by-pass valve.

6. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic press-operating-circuit; a reversing valveoperatively connected in said circuit; a source of fluid pressure; apilot valve operatively connected to said source of iuid pressure;pressure responsive valve-actuating means associated with said reversingvalve; means adapted to rovide fluid communication between the p1lotvalve and said valve actuating means for admitting fluid from saidsource of pressure to said valveactuating means to shift the reversingvalve when the pilot valve is shifted; means for shifting the pilotvalve when the platen approaches the end of its pressing stroke; aby-pass valve in said press operating circuit adapted when open todivert fluid from the reversing valve during continued discharge of thepump; pressure responsive means associated with said by-pass valve andadapted to move the latter to open and closed positions;.means adaptedto afford communication betwcen said source of pressure and saidpressure responsive means; a platenA operated valve interposed in saidlast named means, and movable to either of two positions 'to directpressure iuid from said source of pressure to said pressure responsivemeans to move the by-pass valve to open and to closed positions; meansfor normally maintaining said platen operated valve in one position; andplaten actuated means for moving said valve to its other position.

7. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous dlscharge pump; a surge tank; means forming withthe press, the surge tank, and the pump a high pressure pressoperatinghydraulic circuit; a reversing valve operatively connected in saidcircuit and positioned within the surge tank; a low pressure hydraulicpilot circuit; a pilot valve operatively connected in said low pressurecircuit and positioned outside of the surge tank; pressure responsivevalveactuating means associated with said reversing valve; hydraulicconnections between the pilot valve and said valve actuating means foradmitting fluid from said low pressure circuit to said valve-actuatingmeans to shift the reversing valve when the pilot valve is shifted;means for shifting the pilot valve when the platen approaches the end ofits pressing stroke; a b -pass valve in said high pressure circuit aapted when open to divert the high pressure fluid from the reversingvalve during continued discharge of the pump, said valve beingpositioned within the surge tank; pressure responsive means associatedwith said bypass valve and adapted to move the latter to open and closedpositions; hydraulic oonnections between the pilot circuit and saidpressure responsive means; a platen operated valve interposed in saidhydraulic connections and movable to either of two positions to directpressure fiuid from the low pressure circuit to said pressure responsivemeans to. move the by-pass valve to open and to closed positions, saidplaten operated valve being positioned outside of the surge tank; meansfor normally maintaining said platen operated valve in one position; andplaten actuated means for moving said valve to its other` position.

8. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic circuit; a reversing valve operatively connected insaid circuit for controlling the direction of movement' of the platen;means for moving the reversing valve when the platen reaches the end ofits pressing stroke to effect a return of the platen; a by-pass valveoperatively connected in said circuit and adapted to be opened when theplaten reaches the end of its returnl stroke yfor diverting the pressurefluid from the press to thereby ring the platen to rest at the end ofvthev return stroke thereof simultaneously with the continued dischar eof the draulic means control ed by the platen for i operating saidby-pass valve from its closed position to its fully open position andvice versa; and means for maintaining the platen at rest. y

9. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the pressandthe pump a high pressure press-operating `hydraulic circuit; a.reversing valve operatlvely connected in said circuit; a low pressurehydraulic pilot circuit; a pilot valve operatively connected in said lowpressure circuit; f pressure responsive valve-actuating means-associated with said reversing valve; hydraulic connections between thepilot valve and said valve actuating means for admitting fluid from saidlow pressure circuit to said valve-actuating means to shift thereversing valve when the pilot valve is shifted; means for shifting thepilot valve when the platen approaches the end of its pressing stroke; aby-pass valve in said high pressure Vcircuit adapted when' open todivert the high pressure fluid from the reversing valve during continueddischarge of the pump; pressure responsive means associated with saidby-pass valve and adapted to move the latter to open and closedpositions; hydraulic connections between the pilot circuit and saidpressure responsive means; a platen operated valve interposed in saidhydraulic connections,

and movable to either of two positions to direct pressure fluidl fromthe low pressure circuit to said pressure responsive means to move theby-pass valve to open and to closed positions; means for normallymaintaining said platen operated valve in one position; platen actuatedmeans for moving said valve to its other position; and means connectedin said high pressure circuit for maintaining the platen at rest whenthe by-pass valve is open.

10. The combination with a hydraulic press including a reciprocatoryplaten; of a continuous discharge pump; means forming with the press andthe pump a hydraulic press-operating circuit; a reversing valveoperatively connected in said circuit; a source of fluid pressure; apilot valve operatively connected to said source of fluid pressure;pressure responsive valve-actuat-v ing means associated with saidreversing valve; means adapted to provide Huid communication between thepilot valve and said valve actuating means for admitting fluid from saidsource of fluid pressure to said valve-actuating means to shift thereversing valve when the pilot valve is shifted; means for shifting thepilot valve when the platen by-pass valve operatively connected in Ysaidapproaches the end of its pressing stroke; clrcuit and adapted to placesaid ump in means for diverting pressure fluid from the commlmicationvwith said tank indepenreversing valve when the platen reaches a dentlyof said control valve means; and predetermined point on its returnstroke to means for operating said by-pass valve when thereby bring theplaten to rest simultanethe. platen approaches the end of a return ouslywith the continued discharge of the stroke and irrespective of thepressure in pump; fluid pressure actuated means for said circuit. 1

operating said last named means and a check 15. The combination. with ahydraulic valve interposed in said press operating cir- Ipress includinga reciprocatory platen and cuit between the pump and the. reversing/hydraulic platen actuating means for recipvalve for maintaining theplaten at rest rocating the platen; ofasurge tank; apump; when thepressure fluid divertingmeans is means forming with the platen actuatingopen. means, surge tank, and pumpa hydraulic 11. The combination with ahydraulic mocircuit; control valve means 1n said circuit tor including'a reciprocable ram, and a cofor controlling communication between saidOperating cylinder; 0f a pump; means formtank and said platen actuatingmeans, and ing a hydraulic circuit with said motor and also between saidpump. and said platen acpump; a reversing valve in said circuit fortuatlng means to effect' a complete recipro- -l-O controlling thedirection of movement of said cation of said platenqa vPISSIII@IBSPOIISVQ ram; a normally closed by-pass valve oonby-pass valveoperatively connected in said nected in said circuit and adapted whenCircuit and adapted to place said pump in open to effect free by-passingof Huid at communlcation with said tank independently substantially nopressure; and fluid pressure 0f Sald' control Valve means; and means foractuated means controlled by movement of alltOmatlCally applying fluidpressure to said ram for moving said by-pass valve to Sald by-PBISSValve OI IllOVIlg the latter its fully Open position when the ram ap-lWhen the Elaten appIOaCheS the end of a, proacheg the end 0f a, Stroke,return stro e irrespective of the pressure in 12. The combination with ahydraulic Sald C11Cl1 t y motor including a reciprocable ram and co- In@eStlInOIly whereof, I have hereunto operating power cylinder; of apump; means SllbSCIlbBd by llame. forming a hydraulic circuit with saidpump WALTER ERNST. and motor or operating said ram; a norv mally closedfiuid pressure responsive bypass valve in said circuit; and aram-operated valve for controlling movement of said bypass valve.

v13. The combination with a hydraulic motor including a reciprocable ramand cooperating power cylinder; of a pump; means forming a hydrauliccircuit with said pump and motor for operating said ram; a bypass Valveinterposed between said circuit and an exhaust, said valve including acasing formed with a bore and a balanced piston valve mounted to slidetherein; a pressure responsive double acting piston connected to saidpiston valve, means for supplying iuid under pressure to said piston foroperating the piston valve in both directions; and a ram operated valvefor controlling application of pressure to said piston.

14. The combination with a hydraulic press including a reciprocatoryplaten and hydraulic platen actuating means for reciprocating theplaten; of a surge tank, a pump; means forming with the platen actuatingmeans, surge tank, and pump a hydraulic circuit; control valve means insaid circuit for controlling communication between said tankand saidplaten actuating means, and also between said pump and said platenactuating means to effect a complete reciprocation of said platen; aplaten controlled

